1. Field of Invention
The current invention relates generally to apparatus, systems and methods for generating radio frequency signals. More particularly, the apparatus, systems and methods relate to generating high power radio frequency (RF) pulses or high power microwave pulses. Specifically, the apparatus, systems and methods provide for generating a high power RF or microwave pulse based on a bipolar signal driver.
2. Description of Related Art
Various techniques based on different types of modulators of low frequency signals have been proposed as sources of RF or microwave radiation. The most successful implementations of this concept in high power microwave (HPM) systems to date have been realized by employing various types of nonlinear transmission lines (NLTLs) with dispersion. NLTLs have traditionally been used in high power microwave circuits for generating short transients, as discussed, for example, in I. G. Kataev, Electromagnetic Shock Waves. London: IIlife, 1966. Recently, the possibility of the direct conversion (modulation) of a flat top “video” pulse into an RF Ise during its propagation along a NLTL with dispersion has been considered in several articles and a patent A. M. Belyantsev, et. al. Technical Physics, 40, 820-6 (1995); 43, 80-85 (1998); 45, 747-752 (2000); A. M. Belyantsev and A. B. Kozyrev, International Journal of Infrared and Millimeter Waves, vol. 23, no. 10, pp. 1475-1500, October 2002; H. Ikezi, J. S. DeGrassie, and J. Drake, Applied Physics Letters, 58, 986-7, (1991); N. Seddon, et. al. 2007 IEEE Pulsed Power Conf. Proc., p. 678; N. Seddon and J. Dolan, U.S. Pat. No. 7,498,978 B2; and V. P. Gubanov, et. Al. Technical Physics Letters, vol. 35, no. 7, pp. 626-628 (2009). These techniques are based on the synchronous excitation of RF waves by an electromagnetic shock wave (EMSW) front. NLTLs capable of producing modulation of a video pulse can be implemented either with nonlinear inductances (for example ferrites or other magnetic nonlinear materials) or nonlinear capacitors (nonlinear dielectrics, pin diodes, Schottky diodes, etc.) or both of them as well as with different types of dispersion. For instance, a technique proposed and developed in A. M. Belyantsev, et. al. Technical Physics, 40, 820-6 (1995); 43, 80-85 (1998); 45, 747-752 (2000) and A. M. Belyantsev and A. B. Kozyrev, International Journal of Infrared and Millimeter Waves, vol. 23, no. 10, pp. 1475-1500, October 2002 and experimentally demonstrated in N. Seddon, et. al. 2007 IEEE Pulsed Power Conf. Proc., p. 678. employs NLTLs with spatial dispersion introduced by capacitance cross links and with nonlinearity introduced by saturable inductance of ferrite material, in which magnetization reversal occurs incoherently in strong fields and can be described by the Gyorgy model in E. M. Gyorgy, J. Appl. Phys., vol. 28, no. 9 (1957). Similar approaches can be implemented employing nonlinear dielectric materials. Furthermore, the technique described in U.S. Pat. No. 7,498,978 B2 and V. P. Gubanov, et. Al. Technical Physics Letters, vol. 35, no. 7, pp. 626-628 (2009) takes advantage of temporal dispersion arising during coherent gyromagnetic magnetization rotation in axially magnetized ferrite materials placed into a coaxial line.
Known high power RF and/or microwave pulse generators based on nonlinear transmission line modulators typically use high voltage unipolar pulses (for example video or rectangular pulse generators) as pump pulse generators. Typically, video pulse generators are implemented as high-voltage Blumlein generators. A resulting output pulse consists of damped RF or microwave sinusoid with direct current (dc) and very low frequency components associated with original video pulse. The energy stored in these direct current and very low frequency components is useless (cannot be radiated). Since the portion of energy stored in these components substantially exceeds the energy stored in RF components, the radiating efficiency of system is very low. Furthermore, the pulse repetition rate is limited by thermal and cooling issues, as well as the charge rate available into the high voltage video pulse generator. Moreover, high-voltage Blumlein generators that usually employ spark-gap switches cannot be recharged in a short time period (sub-nanosecond range). Therefore, it is generally not possible in an existing system based on NLTL modulators to generate a train of damped sinusoids to provide high output energy in short period of time. A need, therefore, exists for a high power pulse generator with a high efficiency.